Pending patent application (Ser. No. 06/916,872, "Naturalistic Illumination System" M Terman, B Perlman, and S Fairhurst) describes a system and method that accurately specifies and reproduces outdoor illumination level as a continuous function of time, at any geographic location (latitude, longitude) and at any day of the year. Functional components of the synthesized signal needed to produce the varying illumination levels are direct sunlight, diffuse sky light, moonlight, and starlight. This method and system of that application provides a comprehensive account of naturalistic lighting cycles on the earth's surface.
The computer in the method and system of the foregoing application uses an algorithm which permits creation of said naturalistic illumination cycles by artificial means in remotely positioned environments and at all times of year, or at a proximal environment at a contrasting time of year. Attenuation of maximal outdoor illumination levels by varying degrees of cloud cover is also accommodated. Thus, the prior method and system can be used to present all or part of a naturalistic daily illumination cycle in, for example, a darkened bedroom, an underground living/working environment, a submarine or spacecraft, a light-isolated industrial building or hospital, or an animal care, animal husbandry or fisheries installation. The moonlight producing aspect of said prior method and apparatus has potential application as a bedroom lighting supplement that may control the timing of female hormonal cycles.
Such artificially created light cycles can be used to create a continuously illuminated environment including modulated daylight levels, dawn and dusk light levels spanning civil, nautical, and astronomical twilight ranges, moonlight levels (as a function of lunar phase), and starlight levels (defined as the lowest level of naturally occurring outdoor light, close to darkness). For particular applications, specific components of the continuous 24-hour cycle can be utilized, such as dawn and/or dusk twilight signals, moonlight signal, or daylight signal (sun above horizon), leaving the remaining intervals of the day illuminated at constant arbitrary levels, at spontaneously occurring local levels, or in darkness.
The prior method and apparatus can also be used to specify lighting cycles that deviate from naturally-occurring cycles in specific parameters, such as periodicity (non-24-hour cycles), as may be needed for specific applications. For example, the cycle period can be matched to the intrinsic circadian rhythm of an organism (for example, 25 hr for a human), for investigations of circadian rhythm entrainment outside the confines of the solar day. As a second example, it can move the illumination pattern across latitudes, longitudes, and/or times of the year in gradual or sudden steps. Thus, a traveler could accommodate to lighting conditions at a remote location in preparation for transmeridional flight, as a jet-lag countermeasure; a person adversely affected by the photic consequences of sudden shifts in local clock time in fall and spring could be exposed over successive light cycles to gradually shifted dawn and dusk signals, smoothing the abrupt transition; a person living under adverse winter-time lighting conditions at northerly latitude, could be shifted in stages toward simulated conditions at a more southerly latitude; or a person undergoing night shift work rotation could delay the phase of the dawn signal to late afternoon in preparation for arising after daytime sleep.